7:06 a.m.
On Thu, Mar 04, 2021 at 06:10:12PM +0000, Daniel P. Berrangé wrote:
Signed-off-by: Daniel P. Berrangé <berrange(a)redhat.com>
---
docs/auth.html.in | 368 ----------------------------------------------
docs/auth.rst | 350 +++++++++++++++++++++++++++++++++++++++++++
docs/meson.build | 2 +-
3 files changed, 351 insertions(+), 369 deletions(-)
delete mode 100644 docs/auth.html.in
create mode 100644 docs/auth.rst
diff --git a/docs/auth.html.in b/docs/auth.html.in
deleted file mode 100644
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@@ -1,368 +0,0 @@
-<?xml version="1.0" encoding="UTF-8"?>
-<!DOCTYPE html>
-<html xmlns="http://www.w3.org/1999/xhtml">
- <body>
- <h1>Connection authentication</h1>
- <p>
- When connecting to libvirt, some connections may require client
- authentication before allowing use of the APIs. The set of possible
- authentication mechanisms is administrator controlled, independent
- of applications using libvirt. Once authenticated, libvirt can apply
- fine grained <a href="acl.html">access control</a> to the
operations
- performed by a client.
- </p>
-
- <ul id="toc"></ul>
-
- <h2><a id="Auth_client_config">Client
configuration</a></h2>
-
- <p>
- When connecting to a remote hypervisor which requires authentication,
-most libvirt applications will prompt the user for the credentials. It is
-also possible to provide a client configuration file containing all the
-authentication credentials, avoiding any interaction. Libvirt will look
-for the authentication file using the following sequence:
- </p>
- <ol>
- <li>The file path specified by the $LIBVIRT_AUTH_FILE environment
- variable.</li>
- <li>The file path specified by the "authfile=/some/file" URI
- query parameter</li>
- <li>The file $XDG_CONFIG_HOME/libvirt/auth.conf</li>
- <li>The file /etc/libvirt/auth.conf</li>
- </ol>
-
- <p>
- The auth configuration file uses the traditional
<code>".ini"</code>
- style syntax. There are two types of groups that can be present in
- the config. First there are one or more <strong>credential</strong>
- sets, which provide the actual authentication credentials. The keys
- within the group may be:
- </p>
-
- <ul>
- <li><code>username</code>: the user login name to act as. This
- is relevant for ESX, Xen, HyperV and SSH, but probably not
- the one you want to libvirtd with SASL.</li>
- <li><code>authname</code>: the name to authorize as. This is
- what is commonly required for libvirtd with SASL.</li>
- <li><code>password</code>: the secret password</li>
- <li><code>realm</code>: the domain realm for SASL, mostly
- unused</li>
- </ul>
-
- <p>
- Each set of credentials has a name, which is part of the group
- entry name. Overall the syntax is
- </p>
-
- <pre>
-[credentials-$NAME]
-credname1=value1
-credname2=value2</pre>
-
- <p>
- For example, to define two sets of credentials used for production
- and test machines, using libvirtd, and a further ESX server for dev:
- </p>
-<pre>
-[credentials-test]
-authname=fred
-password=123456
-
-[credentials-prod]
-authname=bar
-password=letmein
-
-[credentials-dev]
-username=joe
-password=hello
-
-[credentials-defgrp]
-username=defuser
-password=defpw</pre>
-
- <p>
- The second set of groups provide mappings of credentials to
- specific machine services. The config file group names compromise
- the service type and host:
- </p>
-
- <pre>
-[auth-$SERVICE-$HOSTNAME]
-credentials=$CREDENTIALS</pre>
-
- <p>
- For example, following the previous example, here is how to
- map some machines. For convenience libvirt supports a default
- mapping of credentials to machines:
- </p>
-
- <pre>
-[auth-libvirt-test1.example.com]
-credentials=test
-
-[auth-libvirt-test2.example.com]
-credentials=test
-
-[auth-libvirt-demo3.example.com]
-credentials=test
-
-[auth-libvirt-prod1.example.com]
-credentials=prod
-
-[auth-libvirt-default]
-credentials=defgrp
-
-[auth-esx-dev1.example.com]
-credentials=dev
-
-[auth-esx-default]
-credentials=defgrp</pre>
-
-
- <p>
- The following service types are known to libvirt:
- </p>
-
- <ul>
- <li><code>esx</code> - used for connections to an ESX or
- VirtualCenter server</li>
- <li><code>hyperv</code> - used for connections to an HyperV
- server</li>
- <li><code>libvirt</code> - used for connections to a libvirtd
- server, which is configured with SASL auth</li>
- <li><code>ssh</code> - used for connections to a remote QEMU
driver
- over SSH</li>
- </ul>
-
- <p>
- Applications using libvirt are free to use this same configuration
- file for storing other credentials. For example, it can be used
- to storage VNC or SPICE login credentials
- </p>
-
- <h2><a id="ACL_server_config">Server
configuration</a></h2>
- <p>
-The libvirt daemon allows the administrator to choose the authentication
-mechanisms used for client connections on each network socket independently.
-This is primarily controlled via the libvirt daemon master config file in
-<code>/etc/libvirt/libvirtd.conf</code>. Each of the libvirt sockets can
-have its authentication mechanism configured independently. There is
-currently a choice of <code>none</code>, <code>polkit</code>,
and <code>sasl</code>.
-The SASL scheme can be further configured to choose between a large
-number of different mechanisms.
-</p>
- <h2><a id="ACL_server_unix_perms">UNIX socket
permissions/group</a></h2>
- <p>
-If libvirt does not contain support for PolicyKit, then access control for
-the UNIX domain socket is done using traditional file user/group ownership
-and permissions. There are 2 sockets, one for full read-write access, the
-other for read-only access. The RW socket will be restricted (mode 0700) to
-only allow the <code>root</code> user to connect. The read-only socket will
-be open access (mode 0777) to allow any user to connect.
-</p>
- <p>
-To allow non-root users greater access, the <code>libvirtd.conf</code> file
-can be edited to change the permissions via the
<code>unix_sock_rw_perms</code>,
-config parameter and to set a user group via the
<code>unix_sock_group</code>
-parameter. For example, setting the former to mode <code>0770</code> and
the
-latter <code>wheel</code> would let any user in the wheel group connect to
-the libvirt daemon.
-</p>
- <h2><a id="ACL_server_polkit">UNIX socket PolicyKit
auth</a></h2>
- <p>
-If libvirt contains support for PolicyKit, then access control options are
-more advanced. The <code>auth_unix_rw</code> parameter will default to
-<code>polkit</code>, and the file permissions will default to
<code>0777</code>
-even on the RW socket. Upon connecting to the socket, the client application
-will be required to identify itself with PolicyKit. The default policy for the
-RW daemon socket will require any application running in the current desktop
-session to authenticate using the user's password. This is akin to
<code>sudo</code>
-auth, but does not require that the client application ultimately run as root.
-Default policy will still allow any application to connect to the RO socket.
-</p>
- <p>
-The default policy can be overridden by creating a new policy file in the
-<code>/etc/polkit-1/rules.d</code> directory. Information on the options
-available can be found by reading the <code>polkit(8)</code> man page. The
-two libvirt actions are named <code>org.libvirt.unix.manage</code> for full
-management access, and <code>org.libvirt.unix.monitor</code> for read-only
-access.
-</p>
- <p>
-As an example, creating
<code>/etc/polkit-1/rules.d/80-libvirt-manage.rules</code>
-with the following gives the user <code>fred</code> full management access
-when accessing from an active local session:
- </p>
-<pre>polkit.addRule(function(action, subject) {
- if (action.id == "org.libvirt.unix.manage" &&
- subject.local && subject.active && subject.user ==
"fred") {
- return polkit.Result.YES;
- }
-});</pre>
- <p>
-Older versions of PolicyKit used policy files ending with .pkla in the
-local override directory
<code>/etc/polkit-1/localauthority/50-local.d/</code>.
-Compatibility with this older format is provided by <a
-href="https://pagure.io/polkit-pkla-compat">polkit-pkla-compat</a>.
As an
-example, this gives the user <code>fred</code> full management access:
- </p>
-<pre>[Allow fred libvirt management permissions]
-Identity=unix-user:fred
-Action=org.libvirt.unix.manage
-ResultAny=yes
-ResultInactive=yes
-ResultActive=yes</pre>
- <h2><a id="ACL_server_sasl">SASL pluggable
authentication</a></h2>
-
- <p>
-Libvirt integrates with the cyrus-sasl library to provide a pluggable authentication
-system using the SASL protocol. SASL can be used in combination with libvirtd's TLS
-or TCP socket listeners. When used with the TCP listener, the SASL mechanism is
-rqeuired to provide session encryption in addition to authentication. Only a very
-few SASL mechanisms are able to do this, and of those that can do it, only the
-GSSAPI plugin is considered acceptably secure by modern standards:
- </p>
-
- <dl>
- <dt>GSSAPI</dt>
- <dd><strong>This is the current default mechanism to use with
libvirtd</strong>.
- It uses the Kerberos v5 authentication protocol underneath, and assuming
- the Kerberos client/server are configured with modern ciphers (AES),
- it provides strong session encryption capabilities.</dd>
-
- <dt>DIGEST-MD5</dt>
- <dd>This was previously set as the default mechanism to use with libvirtd.
- It provides a simple username/password based authentication mechanism
- that includes session encryption.
- <a href="https://tools.ietf.org/html/rfc6331">RFC
6331</a>, however,
- documents a number of serious security flaws with DIGEST-MD5 and as a
- result marks it as <code>OBSOLETE</code>. Specific concerns are
that
- it is vulnerable to MITM attacks and the MD5 hash can be brute-forced
- to reveal the password. A replacement is provided via the SCRAM mechanism,
- however, note that this does not provide encryption, so the SCRAM
- mechanism can only be used on the libvirtd TLS listener.
- </dd>
-
- <dt>PASSDSS-3DES-1</dt>
- <dd>This provides a simple username/password based authentication
- mechanism that includes session encryption. The current cyrus-sasl
- implementation does not provide a way to validate the server's
- public key identity, thus it is susceptible to a MITM attacker
- impersonating the server. It is also not enabled in many OS
- distros when building SASL libraries.</dd>
-
- <dt>KERBEROS_V4</dt>
- <dd>This uses the obsolete Kerberos v4 protocol to provide both
authentication
- and session encryption. Kerberos v4 protocol has been obsolete since the
- early 1990's and has known security vulnerabilities so this will never be
- used in practice.</dd>
- </dl>
-
- <p>
- Other SASL mechanisms, not listed above, can only be used when the libvirtd
- TLS or UNIX socket listeners.
- </p>
-
- <h3><a id="ACL_server_username">Username/password
auth</a></h3>
- <p>
-As noted above, the DIGEST-MD5 mechanism is considered obsolete and should
-not be used anymore. To provide a simple username/password auth scheme on
-the libvirt UNIX socket or TLS listeners, however, it is possible to use
-the SCRAM mechanism. The <code>auth_unix_ro</code>,
<code>auth_unix_rw</code>,
-<code>auth_tls</code> config params in <code>libvirt.conf</code>
can be used
-to turn on SASL auth in these listeners.
- </p>
- <p>
-Since the libvirt SASL config file defaults to using GSSAPI (Kerberos), a
-config change is required to enable plain password auth. This is done by
-editing <code>/etc/sasl2/libvirt.conf</code> to set the
<code>mech_list</code>
-parameter to <code>scram-sha-1</code>.
- </p>
- <p>
-Out of the box, no user accounts are defined, so no clients will be able to
authenticate
-on the TCP socket. Adding users and setting their passwords is done with the
<code>saslpasswd2</code>
-command. When running this command it is important to tell it that the appname is
<code>libvirt</code>.
-As an example, to add a user <code>fred</code>, run
-</p>
- <pre>
-# saslpasswd2 -a libvirt fred
-Password: xxxxxx
-Again (for verification): xxxxxx
-</pre>
- <p>
-To see a list of all accounts the <code>sasldblistusers2</code> command can
be used.
-This command expects to be given the path to the libvirt user database, which is kept
-in <code>/etc/libvirt/passwd.db</code>
-</p>
- <pre>
-# sasldblistusers2 -f /etc/libvirt/passwd.db
-fred(a)t60wlan.home.berrange.com: userPassword
-</pre>
- <p>
-Finally, to disable a user's access, the <code>saslpasswd2</code>
command can be used
-again:
-</p>
- <pre>
-# saslpasswd2 -a libvirt -d fred
-</pre>
- <h3><a id="ACL_server_kerberos">GSSAPI/Kerberos
auth</a></h3>
- <p>
-The plain TCP listener of the libvirt daemon defaults to using SASL for authentication.
-The libvirt SASL config also defaults to GSSAPI, so there is no need to edit the
-SASL config when using GSSAPI. If the libvirtd TLS or UNIX listeners are used,
-then the Kerberos session encryption will be disabled since it is not required
-in these scenarios - only the plain TCP listener needs encryption
-</p>
- <p>
-Some operating systems do not install the SASL kerberos plugin by default. It
-may be necessary to install a sub-package such as
<code>cyrus-sasl-gssapi</code>.
-To check whether the Kerberos plugin is installed run the
<code>pluginviewer</code>
-program and verify that <code>gssapi</code> is listed, e.g.:
-</p>
- <pre>
-# pluginviewer
-...snip...
-Plugin "gssapiv2" [loaded], API version: 4
- SASL mechanism: GSSAPI, best SSF: 56
- security flags:
NO_ANONYMOUS|NO_PLAINTEXT|NO_ACTIVE|PASS_CREDENTIALS|MUTUAL_AUTH
- features: WANT_CLIENT_FIRST|PROXY_AUTHENTICATION|NEED_SERVER_FQDN
-</pre>
- <p>
-Next it is necessary for the administrator of the Kerberos realm to
-issue a principal for the libvirt server. There needs to be one
-principal per host running the libvirt daemon. The principal should be
-named <code>libvirt/full.hostname(a)KERBEROS.REALM</code>. This is
-typically done by running the <code>kadmin.local</code> command on the
-Kerberos server, though some Kerberos servers have alternate ways of
-setting up service principals. Once created, the principal should be
-exported to a keytab, copied to the host running the libvirt daemon
-and placed in <code>/etc/libvirt/krb5.tab</code>
-</p>
- <pre>
-# kadmin.local
-kadmin.local: add_principal libvirt/foo.example.com
-Enter password for principal "libvirt/foo.example.com(a)EXAMPLE.COM":
-Re-enter password for principal "libvirt/foo.example.com(a)EXAMPLE.COM":
-Principal "libvirt/foo.example.com(a)EXAMPLE.COM" created.
-
-kadmin.local: ktadd -k /root/libvirt-foo-example.tab
libvirt/foo.example.com(a)EXAMPLE.COM
-Entry for principal libvirt/foo.example.com(a)EXAMPLE.COM with kvno 4, encryption type
Triple DES cbc mode with HMAC/sha1 added to keytab WRFILE:/root/libvirt-foo-example.tab.
-Entry for principal libvirt/foo.example.com(a)EXAMPLE.COM with kvno 4, encryption type
ArcFour with HMAC/md5 added to keytab WRFILE:/root/libvirt-foo-example.tab.
-Entry for principal libvirt/foo.example.com(a)EXAMPLE.COM with kvno 4, encryption type DES
with HMAC/sha1 added to keytab WRFILE:/root/libvirt-foo-example.tab.
-Entry for principal libvirt/foo.example.com(a)EXAMPLE.COM with kvno 4, encryption type DES
cbc mode with RSA-MD5 added to keytab WRFILE:/root/libvirt-foo-example.tab.
-
-kadmin.local: quit
-
-# scp /root/libvirt-foo-example.tab root@foo.example.com:/etc/libvirt/krb5.tab
-# rm /root/libvirt-foo-example.tab
-</pre>
- <p>
-Any client application wishing to connect to a Kerberos enabled libvirt server
-merely needs to run <code>kinit</code> to gain a user principal. This may
well
-be done automatically when a user logs into a desktop session, if PAM is set up
-to authenticate against Kerberos.
-</p>
- </body>
-</html>
diff --git a/docs/auth.rst b/docs/auth.rst
new file mode 100644
index 0000000000..506e6b5c13
--- /dev/null
+++ b/docs/auth.rst
@@ -0,0 +1,350 @@
+=========================
+Connection authentication
+=========================
+
+.. contents::
+
+When connecting to libvirt, some connections may require client
+authentication before allowing use of the APIs. The set of possible
+authentication mechanisms is administrator controlled, independent
+of applications using libvirt. Once authenticated, libvirt can apply
+fine grained `access control <acl.html>`_ to the operations
+performed by a client.
+
+Client configuration
+====================
+
+When connecting to a remote hypervisor which requires authentication,
+most libvirt applications will prompt the user for the credentials. It is
+also possible to provide a client configuration file containing all the
+authentication credentials, avoiding any interaction. Libvirt will look
+for the authentication file using the following sequence:
+
+* The file path specified by the ``$LIBVIRT_AUTH_FILE`` environment
+ variable.
+* The file path specified by the ``authfile=/some/file`` URI
+ query parameter
+* The file ``$XDG_CONFIG_HOME/libvirt/auth.conf``
+* The file ``/etc/libvirt/auth.conf``
+
+The auth configuration file uses the traditional ``.ini``
+style syntax. There are two types of groups that can be present in
+the config. First there are one or more ``credential``
+sets, which provide the actual authentication credentials. The keys
+within the group may be:
+
+* ``username``: the user login name to act as. This
+ is relevant for ESX, Xen, HyperV and SSH, but probably not
+ the one you want to libvirtd with SASL.
s/want to/want for
...
+For example, to define two sets of credentials used for production
+and test machines, using libvirtd, and a further ESX server for dev:
s/dev/development/
...
+ polkit.addRule(function(action, subject) {
+ if (action.id == "org.libvirt.unix.manage" &&
+ subject.local && subject.active &&; subject.user ==
"fred") {
s/amp;//g
s/; subject/ subject/
...
+
+As noted above, the DIGEST-MD5 mechanism is considered obsolete and should
+not be used anymore. To provide a simple username/password auth scheme on
+the libvirt UNIX socket or TLS listeners, however, it is possible to use
+the SCRAM mechanism. The ``auth_unix_ro``, ``auth_unix_rw``,
+``auth_tls`` config params in ``libvirt.conf`` can be used
s/libvirt.conf/libvirtd.conf/
All of the nits are pre-existing...please fix them in a trivial patch before
pushing.
Reviewed-by: Erik Skultety <eskultet(a)redhat.com>